Organic electronic and optoelectronic have been the focus of growing number of the researchers particularly in the fields of physics and chemistry for more than 50 years. The main attraction of this field comes from the ability to modify the chemical structure of the organic compounds in a way that the properties of the materials could directly be affected. Until the mid-1980s, their stability and performance fell short of those devices based on materials such as silicon or gallium arsenide. This situation was changed since then with the demonstration of a low voltage and efficient thin film light emitting diode, which opened the door of the possibility of using organic thin films for a new generation of electronic and optoelectronic devices. It has now proven that organic thin films are useful in a number of applications. Among them, organic light emitting device (OLED) is the most successful one, which is used now in full-color displays.
In general, two groups of organic materials, small molecules and polymers, are used in electronic and optoelectronic devices. Since polymers can be processed from solutions, they allow low cost fabrication of devices. Polymer electro-luminescent devices are described, for example, WO 2007/134280A1; US2005/01184A1; WO90/13148; US005399502; U.S. Pat. No. 4,356,429.
Understanding of their electronic structure is the key to the design of high performance optical and electronic organic devices, and some important tunings in structure or composition of an organic material can markedly alter its bulk properties. Currently, modification of the molecular structure of the conjugated materials to tune their optoelectronic properties is a challenging topic. Thiophene-based organic materials are among the most promising compounds with tuneable functional properties by proper molecular engineering. For example, thiophenes and their oligomers and polymers are not proper materials for applications in light emitting devices as they have low electron affinities and low solid-state photoluminescence efficiencies. On the other hand, converting oligothophenes into the corresponding oligothiophene-S,S-dioxides has been shown to be useful for increasing both thin film photoluminescence efficiencies and molecular energy levels.
The use of boron to alter the properties of organic electronics and optoelectronics materials has started recently and given interesting results. The reason for that is the presence of empty pz orbital of boron which behaves as strong electron withdrawing atom when it makes three bonds. It delocalizes electrons strongly when integrated to “π” systems. In organic materials chemistry, conjugated organoborane polymers are now considered as new class of organic materials with their widespread applications in electronics, optoelectronics and sensors.
In OLED technology, white light is generally obtained with multi-emissive layers to provide the three main colors, i. e. blue, green and red, combination of which gives white color. On the other hand, obtaining white color from one emissive layer is a challenge. Emission from such material needs to cover wide range of visible region.
Materials incorporating thiophene, thiophene derivatives and boron tend to emit white light (M. Mazzeo, Adv. Mater. 2005, 17, 34). Thus, it would be desirable developing materials having thiophene, thiophene derivatives and boron to obtain white light for organic light emitting diodes.